Delivery of a baby is followed by separation of the placenta from the uterine wall, usually resulting in a significant loss of blood. Fortunately, the uterus is resistant to anoxic damage caused by reduced blood flow. For example, uterine muscle is typically poorly perfused during labor contractions, yet typically suffers no lasting ill effects from this situation. However, hemorrhage from the uterus following delivery may cause loss of a significant fraction of the mother's blood if it is not stopped quickly. Blood loss from prolonged hemorrhage following delivery presents a serious threat to the life and health of the mother.
The muscular contractions and hormonal changes accompanying vaginal delivery promote rapid cessation of postpartum hemorrhage. However, caesarian delivery is typically not accompanied by such contractions and hormonal changes, and also entails physical injury to the uterus additional to that caused by placental separation. Delivery by caesarian section is thus often accompanied by hemorrhage from the placental attachment site and from the uterine incision required for delivery of the infant. Medical intervention is typically required to reduce blood loss following caesarian deliveries.
The primary blood supply to the uterus, both in the non-gravid uterus and in the pregnant uterus, is from the uterine arteries. A small communicating artery arising from each ovarian artery reaches uterus but in gravid and non-gravis states supplies less than 10% of uterine blood flow. The uterine arteries arise from the internal iliac arteries and reach the uterus through the base of the broad ligament in a space that can not be seen from a surgical perspective looking down on the uterus from within the peritoneal cavity or from a gynecological perspective looking up at the cervix from the vagina. The uterine arteries are, therefore, not visible.
Once the uterine arteries reach the uterus, they give rise to a large ascending branch that supplies the uterus and a smaller descending branch that supplies the cervix. These branches, in turn, give rise to anterior and posterior arcuate arteries. Right and left anterior arcuate arteries anastomose in the anterior sagittal midline of the uterus; posterior arcuate arteries, in the posterior sagittal uterine midline. Consequently, to reduce blood loss following caesarian delivery from the hysterotomy site and from the placenta attachment site, right and left uterine arteries must both be occluded.
Attempts have been made to reduce caesarian delivery blood loss. One method has been to initiate uterine contractions by administering oxytocin or oxytocin-like drugs following caesarian delivery. Another method has been blind clamping of the uterine and ovarian arteries using rubber covered arterial clamps, which was proposed as early as 1922. Similarly, intestinal clamps have been applied to the uterus along its right and left lateral borders, across the entire broad ligament, to minimize caesarian blood loss. Another method includes bilateral surgical ligation of the internal iliac arteries to diminish hemorrhage following caesarian delivery. Bilateral surgical ligation of the uterine arteries, or of the ascending branches of the uterine arteries, to reduce hemorrhaging has been performed from abdominal cavity and from transvaginal approaches. Intravascular balloon occlusion of the aorta and embolic occlusion of the uterine arteries have also been used to treat caesarian hemorrhage. However, all of these methods have met with only limited adoption for a variety of reasons.
For example, many physicians do not possess the training or equipment necessary to perform catheter-based uterine artery embolization under radiologic direction. In addition, such treatments are not appropriate in the case of caesarian hemorrhage, where rapid treatment can be critical and arterial catheterization may not be practical.
Location of the uterine arteries in a patient immediately following a caesarian delivery may be difficult; in addition to being located within the broad ligament that supports the uterus, the uterine arteries are near or within the caesarian surgical field, and so are typically covered with blood, amniotic fluid, and the like which can impede visual identification and medical access following caesarian section. Rapid identification and location of the uterine arteries is required in order to prevent unchecked hemorrhage.
Accordingly, there is need for devices and methods to control blood flow in blood vessels such as uterine arteries by physicians with little training in a simple medical setting or environment.